如何在mysql..中获取缺席的用户列表？

Question

我有如下表格

employees
-----------------------
empId  Name   MobileNumber
1      Name1  12345
2      Name2  123456
3      Name3  1234567
4      Name4  12345678

attendance
-------------------------------------------
Id    MobileNumber    Type    attendance_datetime
1     12345           IN      2017-05-31 10:04:42
2     123456          IN      2017-05-31 10:05:29
3     1234567         IN      2017-05-31 10:06:15
4     12345           OUT     2017-05-31 18:05:15
5     123456          OUT     2017-05-31 18:10:15
6     1234567         OUT     2017-05-31 18:15:15

我想获取特定日期的缺席用户列表如何获取？

我试过下面的查询，但没有得到结果。

select * from employees e,attendance a where e.MobileNumber = a.MobileNumber AND DATE(a.attendance_datetime) =  str_to_date('31-05-2017', '%d-%m-%Y') 

Answer 1

您需要使用左外连接：

SELECT * FROM employees e
LEFT JOIN attendance ON employees.MobileNumber = attendance.MobileNumber
AND DATE(attendance_datetime) = '2017-05-31'
WHERE attendance.Id IS NULL